Persistent Insta-Kill

Since the 2.1.05 patch to accommodate the RevolutionDLC, this Persistent Perk has been discovered. To achieve this, you have to collect a dropped Insta-Kill, and not kill a single zombie until the Power Up goes away. Upon doing this, a green mist will appear signifying that you have attained it. Once the next Insta-Kill Power Up drops and you get it, a secondary marker will appear above the primary one on your screen, save for being red and slightly smaller. The new version of the Power Up makes any zombie that touches you explode, while you sustain no damage. The catch to this Power Up is that it only lasts half the time of a regular Insta-Kill, and once the red version vanishes, you cannot kill any zombies until the primary Insta-Kill also vanishes. Otherwise you will lose it, and have to go through the aforementioned steps to get it back.